1. Field of the Invention
The present invention relates to a technology of changing and controlling arbitrarily the orientation of a ferroelectric film to be crystallized.
2. Description of a Related Art
A conventional method for manufacturing Pb(Zr,Ti)O3 (hereinafter, referred to as “PZT”) perovskite-type ferroelectric ceramics will be described.
On a 4-inch Si wafer, a SiO2 film having a thickness of 300 nm is formed, and, on the SiO2 film, a TiOx film having a thickness of 5 nm is formed. Next, on the TiOx film, a Pt film having a thickness of 150 nm oriented, for example, in (111) is formed, and, on the Pt film, a PZT sol-gel solution is spin-coated with a spin coater. The spin condition at this time is such that the wafer is rotated for 30 seconds at a rotation rate of 1500 rpm and for 10 seconds at a rotation rate of 4000 rpm.
Next, the coated PZT sol-gel solution is heated and held on a hot plate at 250° C. for 30 seconds to be dried and the moisture was eliminated, and, after that, in addition, the solution is heated and held for 60 seconds on a hot plate kept at high temperature of 500° C., and thus temporary calcinations is performed. By repetition of these a plurality of times, a PZT amorphous thin film having a thickness of 150 nm is produced.
Subsequently, annealing treatment was performed on the PZT amorphous thin film by using a pressurizing-type lamp annealing apparatus (RTA: rapidly thermal anneal), to crystallize the PZT. The crystallization annealing at this time was performed under conditions in which the thin film was heated up to 700° C. at a temperature increase rate of 100° C./sec and held for 1 min, at respective oxygen partial pressures of 1 atm, 5 atm and 10 atm. The PZT film thus crystallized is composed of a perovskite structure (see, for example, Patent Document 1 (WO 2006/087777)).
PZT films crystallized at each of oxygen partial pressures of the above-described 1 atm, 5 atm and 10 atm were evaluated by X-ray diffraction (hereinafter, represented as “XRD”) measurement. As a result, even by simply changing the oxygen partial pressure, no change occurred in the orientation of the PZT film crystal, which did not allow control of the orientation of the PZT film.
FIG. 8 is a drawing showing an XRD pattern of the PZT film crystallized at an oxygen partial pressure of the above-described 10 atm, in which the vertical axis shows an XRD reflection intensity and the horizontal axis shows a rotation angle 2θ. From FIG. 8, it is known that the PZT film is crystallized, but in the industrial world, a ferroelectric material film having further higher crystallinity is required.